Semiconductor integrated circuit device

ABSTRACT

With an ultrasound pulser suitable for application to a medical ultrasound system, and so forth, a high voltage power supply of a transducer drive circuitry, on both high potential and low potential sides, is rendered variable in a range of 0 V on the order of ±200 V, thereby implementing a semiconductor integrated circuit wherein a plurality of the ultrasound pulsers corresponding to a plurality of channels, respectively, are integrally formed on a small area. The ultrasound pulser has a configuration wherein, in a MOSFET gate drive circuitry, an input voltage pulse is converted into a current pulse, and the current pulse is converted again into a voltage pulse on the basis of a high potential side voltage +HV, and a low potential side voltage −HV, applied to a transducer drive circuitry, whereupon voltage level shift in the input voltage pulse is attained, and a voltage pulse swing of an output buffer of the MOSFET gate drive circuitry receiving a shifted voltage pulse is generated by the MOSFET gate drive circuitry similarly on the basis of the high potential side voltage +HV, and the low potential side voltage −HV, applied to the transducer drive circuitry. The MOSFET gate drive circuitry is DC-coupled with the transducer drive circuitry.

CLAIM OF PRIORITY

The present application claims priority from Japanese application JP 2007-090207 filed on Mar. 30, 2007, the content of which is hereby incorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to a semiconductor integrated circuit device having a high voltage high-speed power switching circuit, and a high-voltage resistant high power driver circuit, and in particular, to a semiconductor integrated circuit device with high-voltage resistant elements and low-voltage resistant elements making up an ultrasound pulser for a medical ultrasound system, integrated on one and the same substrate such as a monocrystalline silicon.

BACKGROUND OF THE INVENTION

There has been available a conventional pulser for a medical ultrasound system having a drive circuitry for converting a predetermined input pulse into a high-voltage pulse to be thereby sent out, and an output transistor to be driven for switching by the high-voltage pulse, for sending out an output pulse for oscillation to an ultrasonic transducer (refer to, for example, JP-B No. 06(1994)-53113). Besides, there has been available a driver (refer to, for example, JP-A No. 2005-340624 and JP-A No. 2000-156495) for driving a plasma display panel, or a pulser similarly having a driver circuitry disposed in a front stage, and an output transistor connected to a succeeding stage thereof, in a driver (refer to, for example, JP-A No. 11(1999)-205112) for driving a high-voltage resistant power integrated circuit for household appliance use, automobiles use, industrial use, and so forth.

Further, there has been available a conventional pulser for a medical ultrasound system (refer to, for example, Supertex Inc., HV732 data sheet) comprising a gate drive circuitry made up of voltage level translators, and voltage buffers, for receiving logical pulses to thereby drive a gate unit in a succeeding stage, and a transducer drive circuitry made up of an output transistor and the gate unit including a clamping circuitry, for driving an ultrasonic transducer in a succeeding stage, wherein the gate drive circuitry is coupled to the transducer drive circuitry via capacitors.

SUMMARY OF THE INVENTION

With transmitter/receiver (Tx/Rx) for use in the medical ultrasound system, further integration for the purposes of achieving enhancement in image resolution by adoption of further multi-channels, and acquisition of three-dimensional images has been continuously promoted. FIG. 4 is a block diagram of a driver, obtained by reconsidering FIG. 1 disclosed in JP-B No. 06(1994)-53113 from an inventor's own point of view prior to the present invention. Further, FIG. 5 is a block diagram of a driver, obtained by reconsidering the representative drawing described in Supertex Inc., HV732 data sheet from the inventor's own point of view prior to the present invention. With those drivers, there has been the demand for multi-channel integration by taking a circuit configuration shown in FIG. 4 or FIG. 5, as a unit channel, however, such integration is difficult to implement because high-voltage operating parts, and low-voltage operating parts are mixedly present in the circuit configuration, and it has therefore become a challenge to implement high-density mounting through the multi-channel integration by solving this problem. Further, an output pulse swing of a driver need be variable in a range of 0 V on the order of ±200 V because a necessary output pulse swing varies depending on a difference between ultrasonic transducer types with respect to voltage—sound-pressure conversion efficiency, a diagnosis block, a diagnostic method, and so forth, and a channel as a damper is normally operated at 0 V.

In JP-B No. 06(1994)-53113, there is described the pulser for the medical ultrasound system wherein a gate drive circuitry for receiving logical pulses to thereby drive a gate unit in a succeeding stage is DC-coupled to a transducer drive circuitry for driving an ultrasonic transducer. As shown in FIG. 4, there is described an example of a driver capable of achieving an output pulse with a fixed swing of Rc/Ra*(VIH−VIL), proportional to an input pulse swing, by use of high-voltage resistant npn bipolar transistors, and a high-voltage resistant n-channel MOSFET (MOS field effect transistor). In the drawings shown hereinafter, a transistor surrounded by a circle indicates a high-voltage resistant transistor while a transistor not in a circle indicates a low-voltage resistant transistor.

The circuitry shown in JP-B No. 06(1994)-53113 is the driver wherein the gate drive circuitry is DC-coupled to the transducer drive circuitry. With this configuration, an external capacitor is not required, and there is no need for an output terminal of the gate drive circuitry, and an input terminal of the transducer drive circuitry, required for connection with the external capacitor, so that it is a configuration wherein the multi-channel integration can be readily implemented, however, with this circuit style, it is necessary that all the transistors should be high-voltage resistant transistors. In general, a layout area of the high-voltage resistant transistor, on a semiconductor substrate, is fairly larger than that of the low-voltage resistant transistor, which poses a barrier against promotion of the multi-channel integration. Further, since an output pulse swing becomes Rc/Ra*(VIH−VIL) proportional to the input pulse swing, it is necessary to render the input pulse swing variable to render the output pulse swing variable. That is, a variable width of the output pulse swing is dependent on a variable width of the input pulse swing, and, for example, in the case where it has been decided that Rc/Ra can output the output pulse swing at not lower tan 100 V, a problem has been encountered in that it is, in theory, difficult to produce a pulse with a small swing on the order of several V. In this respect, the same applies to respective driver configurations described in Patent Documents 2 to 4.

Meanwhile, in Supertex Inc., HV732 data sheet, there is described the pulser for the medical ultrasound system wherein the gate drive circuitry for receiving the logical pulses to thereby drive the gate unit in the succeeding stage is AC-coupled to the transducer drive circuitry for driving the transducer. As shown in FIG. 5, there is described an example of a driver wherein low-voltage resistant CMOSFETs (Complementary MOSFETs) are used in the gate drive circuitry while high-voltage resistant CMOSFETs are used in the transducer drive circuitry, the gate drive circuitry drives the transducer drive circuitry via external capacitors, and a variable output pulse swing is implemented by varying voltages +HV, and −HV, applied to the transducer drive circuitry.

The circuitry shown in Supertex Inc., HV732 data sheet is the driver wherein the gate drive circuitry is AC-coupled to the transducer drive circuitry via the external capacitors. With this circuit style, it becomes possible to render the output pulse swing variable in the range of 0 V on the order of ±200 V. However, since two terminals are required for connection with one external capacitor, a problem has been encountered in that channel integration is limited due to an increase in the number of total terminals of a package, and constraints imposed on mounting of the external capacitors.

It is therefore an object of the invention to provide an ultrasound pulser wherein outputs of a MOSFET gate drive circuitry are DC-coupled with inputs of a transducer drive circuitry, respectively, and output pulses, on both high potential and low potential sides, are rendered variable in a range of 0 V on the order of ±200 V by use of low-voltage resistant transistors advantageous in terms of a layout area of a semiconductor substrate wherever possible.

An example of a representative configuration of the invention is described as follows. That is, the invention provides in its one aspect a semiconductor integrated circuit comprising input terminals, a first drive circuitry connected to the terminals, for converting a first voltage pulse signal having a first reference potential, inputted from the respective terminals, into a second voltage pulse signal having a second reference potential higher than the first reference potential to be thereby outputted, a second drive circuitry connected to outputs of the first drive circuitry, for generating a fourth voltage pulse signal with a voltage swing based on a potential difference between the second reference potential, and a ground potential, for driving an external output load on the basis of the second voltage pulse signal inputted from the respective outputs of the first drive circuitry to be thereby outputted, and an output OUT connected to outputs of the second drive circuitry, for outputting the fourth voltage pulse signal outputted by the second drive circuitry to the external output load, wherein the first drive circuitry is integrated with the second drive circuitry into one unit on a single semiconductor substrate, the outputs of the first drive circuitry are mutually DC-coupled with inputs of the second drive circuitry, respectively, and the first drive circuitry includes voltage-to-current converters for converting a third voltage pulse signal based on the first voltage pulse signal into a current pulse signal, respectively, and current-to-voltage converters for converting the current pulse signals inputted from respective outputs of the voltage-to-current converters into the second voltage pulse signal, respectively, such that reference potentials of the respective current pulse signals are changed from the first reference potential to the second reference potential.

With the invention, an ultrasound pulser having an output pulse swing variable range of 0 V on the order of ±200 V, suitable for application to a medical ultrasound system, can be implemented on a semiconductor substrate small in area, leading to implementation of the ultrasound pulsers in the form of a semiconductor integrated circuit wherein a plurality of channels are integrated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing one embodiment of an ultrasound pulser to which the invention is applied;

FIG. 2 is a view showing a specific configuration example of the ultrasound pulser to which the invention is applied;

FIG. 3 is a view showing an example of a multi-channel integrated driver circuitry comprising a plurality of channels, the ultrasound pulser shown in FIG. 1, serving as one unit of the channel;

FIG. 4 is a block diagram of a driver, obtained by reconsidering FIG. 1 disclosed in JP-B No. 06(1994)-53113 from an inventor's own point of view prior to the present invention; and

FIG. 5 is a block diagram of a driver, obtained by reconsidering the representative drawing described in Supertex Inc., HV732 data sheet from the inventor's own point of view prior to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the invention are described hereinafter with reference to the accompanying drawings. Circuit elements making up respective blocks of an embodiment include a low-voltage resistant CMOSFET, high-voltage resistant CMOSFET, diode, resistor, and capacitor, well known, and those circuit elements are formed on a single semiconductor substrate such as a monocrystalline silicon by an IC technology.

First Embodiment

FIG. 1 is a block diagram showing a first embodiment of an ultrasound pulser to which the invention is applied. The driver according to the present embodiment is implemented as a semiconductor integrated circuit having the following features. More specifically, the semiconductor integrated circuit according to the present embodiment comprises input terminals INP, INN, a first drive circuitry 10 connected to the respective terminals INP, INN, for converting a first voltage pulse signal having a first reference potential inputted from the respective terminals INP, INN into a second voltage pulse signal having a second reference potential higher than the first reference potential to be thereby outputted, a second drive circuitry 20 connected to outputs of the first drive circuitry 10, for generating a fourth voltage pulse signal for driving an external output load 30 on the basis of the second voltage pulse signal inputted from the respective outputs of the first drive circuitry 10 to be thereby outputted, and an output OUT connected to outputs of the second drive circuitry 20, for outputting the fourth voltage pulse signal outputted by the second drive circuitry 20 to the external output load 30. The first drive circuitry 10 is integrated with the second drive circuitry 20 into one unit on a single semiconductor substrate, and the outputs of the first drive circuitry 10 are mutually DC-coupled with inputs of the second drive circuitry 20, respectively. The first drive circuitry 10 includes voltage-to-current converters 104, 106, for converting a voltage pulse signal based on the first voltage pulse signal into a current pulse signal, respectively, and current-to-voltage converters 108, 110, for converting the current pulse signals inputted from respective outputs of the voltage-to-current converters 104, 106 into a second voltage pulse signal, respectively.

The second drive circuitry 20 is normally higher in voltage resistance than the first drive circuitry 10. Further, the first drive circuitry 10 preferably further comprises voltage level translators 100, 102, interconnecting the respective terminals INP, INN, and respective inputs of the voltage-to-current converters 104, 106, respectively. In this case, the first voltage pulse signal having the first reference potential is converted into a third voltage pulse signal having the first reference potential through the respective voltage level translators 100, 102.

The semiconductor integrated circuit according to the present embodiment preferably further comprises third power supply voltage terminals +VDD, −VDD, made up such that a third power supply voltage is applied thereto, and second power supply voltage terminals +HV, −HV, made up such that a second power supply voltage higher than the third power supply voltage is applied thereto. In this case, the first drive circuitry 10 is connected to a first power supply voltage terminal VLL, the second power supply voltage terminals +HV, −HV, and the third power supply voltage terminals +VDD, −VDD, respectively, and the second drive circuitry 20 is connected to the second power supply voltage terminals +HV, −HV, respectively. The second drive circuitry 20 generates the fourth voltage pulse signal from the second voltage pulse signal on the basis of the second power supply voltage applied to the second drive circuitry 20 via the second power supply voltage terminals +HV, −HV, respectively. Further, the first drive circuitry 10 preferably comprises an internal power supply circuit including a source follower, for generating an input gate voltage swing of the second drive circuitry 20 on the basis of the second power supply voltage applied to the second drive circuitry 20.

When the semiconductor integrated circuit according to the present embodiment is applied to an ultrasound pulser for a medical ultrasound system, the external output load 30 is an ultrasonic transducer, the second drive circuitry 20 is a transducer drive circuitry, and the first drive circuitry 10 is a MOSFET gate drive circuitry for driving input gates 200, 202, making up the second drive circuitry 20. Accordingly, it follows that the ultrasound pulser for the medical ultrasound system is comprised of the MOSFET gate drive circuitry 10, and the transducer drive circuitry 20.

It can be taken that the semiconductor integrated circuit according to the present embodiment comprises a first drive circuitry 10 having a first voltage resistance, and a second drive circuitry 20 connected to a back stage of the first drive circuitry 10, having a second voltage resistance higher than the first voltage resistance. In this case, the first drive circuitry 10 comprises voltage-to-current converters 104, 106, for converting an input voltage signal into a current signal, respectively, and current-to-voltage converters 108, 110, for converting the current signal into a voltage signal, respectively. An element having the second voltage resistance is used at respective spots of the converters 104, 106, 108, 110, where the second voltage resistance is required. In this case, a voltage signal with a voltage pulse swing based on an output voltage keeping a fixed difference from a voltage necessary for driving the second drive circuitry 20 is preferably outputted to the second drive circuitry 20.

The first drive circuitry 10 is preferably made up so as to be operated by first, second, and third operating voltages, respectively, having a circuit for generating a second potential having a predetermined potential difference on the basis of a predetermined third potential. In this case, the second drive circuitry 20 is operated at the second potential as the operating voltage, and signal transmission from the first drive circuitry 10 to the second drive circuitry 20 is executed by the respective voltage-to-current converters 104, 106, for converting the input voltage signal into the current signal, and the respective current-to-voltage converters 108, 110, for converting the current signal into a voltage signal.

With the present embodiment, the ultrasonic transducer 30 connected to the output terminal OUT may be driven by a bipolar voltage output pulse in form protruding upward and downward, as shown in, for example, FIG. 1.

The present ultrasound pulser is comprised of the MOSFET gate drive circuitry 10, and the transducer drive circuitry 20. The MOSFET gate drive circuitry 10 preferably comprises the voltage level translators 100, 102, connected to, for example, an input logic control terminal INP of the high voltage Pch MOSFET and an input logic control terminal INN of the high voltage Nch MOSFET, respectively, the voltage-to-current converters 104, 106, and the current-to-voltage converters 108, 110. The transducer drive circuitry 20 preferably comprises for example, a high voltage resistant p-channel MOSFET 200, and a high voltage resistant n-channel MOSFET 202, connected to outputs GP, GN of the MOSFET gate drive circuitry 10, respectively, Zener diodes 212, 214, for protection of respective gates of the MOSFETs 200, 202, resistors 208, 210, and high voltage resistant diodes 204, 206.

FIG. 2 shows a specific configuration example of the ultrasound pulser shown in FIG. 1. In FIG. 2, reference numerals 10, 20, 30, 100, 102, 104, 106, 108, 110, 200, 202, 204, 206, 208, 210, 212, and 214 each indicate a circuit block, and a circuit element, corresponding to each of the same reference numerals in FIG. 1. First, there is described hereunder a signal path from the input logic control terminal INP of the high voltage Pch MOSFET to the high voltage resistant p-channel MOSFET 200.

The voltage level translator 100 converts a voltage pulse swing of VLL, inputted to INP, into VDD, equal to an operating power supply voltage of the voltage-to-current converter 104 in the next stage. That is, a high level input voltage Vih=VLL, and a low level input voltage Vil=0 V, at INP, are converted into a high level output voltage Voh=VDD, a low level output voltage Vol=0 V, respectively, at an output 112 of the voltage level translator 100. Such conversion is implemented by a latch circuit 114. The voltage-to-current converter 104 converts the output voltage pulse signal of the voltage level translator 100 in a preceding stage into the current pulse signal. The voltage-to-current converter 104 is comprised of resistors R1, R2, R3, current mirror circuits 116, 118, and a high voltage resistant n-channel MOSFET 120. When the output 112 of the voltage level translator 100 is at a high level, the current mirror circuit 116 has a reference voltage at VDD, so that no potential difference occurs to the resistor R1, and no current flows to a copy source of the current mirror circuit 116. On the other hand, when the output 112 is at a low level, a potential difference of VDD−2*Vgs occurs across both ends of the resistor R1, resulting in flow of current expressed by (VDD−2*Vgs)/R1. This Vgs represents a gate—source voltage of a low voltage resistant p-channel MOSFET as a constituent of the current mirror circuit 116. That is, a voltage pulse at the output 112 is converted into a current pulse by the resistor R1. The current pulse is returned to the current mirror circuit 118 having a source-side reference voltage at −VDD by the current mirror circuit 116, and current copying is executed. A high voltage resistant n-channel MOSFET 120 is inserted to prevent a high voltage not lower than a absolute rating from being applied between the source and the drain of a low voltage resistant n-channel MOSFET as a copy destination of the current mirror circuit 118, and the resistors R3, R4 are set such that a gate potential expressed by (R4/(R3+R4)−1)*VDD can cause the high voltage resistant n-channel MOSFET 120 to adequately operate.

With the present configuration example, the current mirror circuits 116, 118 each are shown in cascade configuration to improve accuracy in current copying by the current mirror circuits 116, 118, respectively. The same applies to current mirror circuits 128, 146, 158, to be described hereinafter.

The current-to-voltage converter 108 converts the current pulse signal outputted by the voltage-to-current converter 104 in a preceding stage into the voltage pulse signal having a voltage pulse swing |VGSp|, and a high level output voltage Voh=+HV, equal to a voltage +HV applied to a source terminal of the high voltage resistant p-channel MOSFET 200 of the transducer drive circuitry 20 in the next stage. Herein, |VGSp| refers to a voltage applied between the source and the gate of the high voltage resistant p-channel MOSFET 200, optimal to operate the same. The current-to-voltage converter 108 comprises a block 122 where current-to-voltage conversion, and buffering are executed, and a block 124 where the swing |VGSp| for driving the gate of the high voltage resistant p-channel MOSFET 200 of the transducer drive circuitry 20 is generated with +HV as a reference potential. The current pulse generated by the voltage-to-current converter 104, described as above, is again converted into a voltage pulse by a resistor R7 of the block 122. If a mirror ratio of either of the current mirror circuits 116, 118 is 1:1, an swing of the voltage pulse converted by the resistor R7 is expressed by (VDD−2*Vgs)*R7/R1. This voltage pulse is inputted to a buffer 126 of the block 122, and the swing of this voltage pulse is normally set to the same as |VGSp|. Since a swing of an output voltage GP of the buffer 126 is the swing for driving the gate of the high voltage resistant p-channel MOSFET 200, as described above, the swing of the output voltage GP need be |VGSp, and a low level output voltage +HV″|VGSp|, decided at a node 132 of the buffer 126, is generated in the block 124. The block 124 comprises a current mirror circuit 128, resistors R5, R6, capacitors C1, C2, a high voltage resistant n-channel MOSFET 130, and a high voltage resistant p-channel MOSFET 136. Current flowing to a copy source of the current mirror circuit 128 is expressed by (VDD−2*Vgs)/R6. This Vgs represents a gate-source voltage of a low voltage resistant n-channel MOSFET as a constituent of the current mirror circuit 128. If a mirror ratio of the current mirror circuit 128 is 1:1, a potential at a node 134, converted by the resistor R5, is expressed by +HV−(VDD−2*Vgs)*R5/R6. The potential at the node 134 is decided such that a potential at the node 132 turns to +HV−|VGSp|, as described above. More specifically, R5, and R6 are decided so as to satisfy (VDD−2*Vgs)*R5/R6=|VGSp|+|Vgs136|. This |Vgs136| refers to a gate—source voltage of the high voltage resistant p-channel MOSFET 136 to execute operation as a source follower. The high voltage resistant n-channel MOSFET 130 is inserted to prevent a high voltage not lower than a absolute rating from being applied between the source and the drain of a low voltage resistant n-channel MOSFET as a copy destination of the current mirror circuit 128, and the resistors R3, R4 are set such that a gate potential expressed by (R4/(R3+R4)−1)*VDD can cause the high voltage resistant n-channel MOSFET 130 to adequately operate, as is the case with the high voltage resistant n-channel MOSFET 120. The capacitor C1 is inserted for the purpose of stabilization of a gate potential of the high voltage resistant p-channel MOSFET 136. The capacitor C2 is inserted between the node 132 as an output of the source follower, and +HV, functioning as a bypass capacitor for supplying instantaneous carrying current consumed by the buffer 126 with an output drive capacity thereof, enhanced to drive the gate of the high voltage resistant p-channel MOSFET 200.

With the current mirror circuits 116, 118, −VDD is a source side reference voltage, so that the signal path from the input logic control terminal INP of the high voltage Pch to the high voltage resistant p-channel MOSFET 200 can be operated as a channel as a damper of +HV=0 V, and +HV is optionally variable in the range of 0 V on the order of +200 V.

Now, there is described hereunder a signal path from the input logic control terminal INN of the high voltage Nch MOSFET to the high voltage resistant n-channel MOSFET 202. The principle behind this signal path is basically the same as that behind the signal path from the input logic control terminal INP of the high voltage Pch MOSFET to the resistant p-channel MOSFET 200.

In FIG. 2, the voltage level translator 102 converts the voltage pulse swing of VLL, inputted to INN, into VDD, equal to an operating power supply voltage of the voltage-to-current converter 106 in the next stage. That is, the high level input voltage Vih=VLL, and the low level input voltage Vil=0 V, at INN, are converted into the low level output voltage Vol=0 V, and the high level output voltage Voh=VDD, respectively, at an output 140 of the voltage level translator 102. Such conversion is implemented by a latch circuit 142.

The voltage-to-current converter 106 converts an output voltage pulse signal of the voltage level translator 102 in a preceding stage into a current pulse signal. The voltage-to-current converter 106 is comprised of a buffer 144, resistors R8, R9, R10, a current mirror circuit 146, and a high voltage resistant p-channel MOSFET 148. When an output 140 of the voltage level translator 102 is at a high level, the current mirror circuit 146 has a reference voltage at VDD, so that no potential difference occurs to the resistor R8, and no current flows to a copy source of the current mirror circuit 146. On the other hand, when the output 140 is at a low level, the potential difference of VDD−2*Vgs occurs across both ends of the resistor R8, resulting in flow of current expressed by (VDD−2*Vgs)/R8. This Vgs represents a gate—source voltage of a low voltage resistant p-channel MOSFET as a constituent of the current mirror circuit 146. That is, a voltage pulse at the output 140 is converted into a current pulse by the resistor R8. The high voltage resistant p-channel MOSFET 148 is inserted to prevent a high voltage not lower than a absolute rating from being applied between the source and the drain of a low voltage resistant p-channel MOSFET as a copy destination of the current mirror circuit 146, and the resistors R9, R10 are set such that a gate potential expressed by R10/(R9+R10)*VDD can cause the high voltage resistant p-channel MOSFET 148 to adequately operate. With the voltage-to-current converter 106, there is no need for current return corresponding to that for the current mirror circuit 118 of the voltage-to-current converter 104 for control of the voltage output pulse in the form protruding upward. Accordingly, the buffer 144 for compensating for propagation delay occurring due to the current return, serving as a delay buffer, is inserted in the signal path, thereby compensating for a difference in propagation delay time between the present signal path, and the signal path for the voltage output pulse in the form protruding upward.

The current-to-voltage converter 110 converts the current pulse signal outputted by the voltage-to-current converter 106 in a preceding stage into a voltage pulse signal having a voltage pulse swing VGSn, and a low level output voltage Vol=−HV equal to a voltage −HV applied to a source terminal of the high voltage resistant n-channel MOSFET 202 of the transducer drive circuitry 20 in the next stage. Herein, VGSn refers to a voltage applied between the source and the gate of the high voltage resistant p-channel MOSFET 202, optimal to operate the same. The current-to-voltage converter 110 comprises a block 150 where current-to-voltage conversion, and buffering are executed, and a block 152 where the swing VGSn for driving the gate of the high voltage resistant n-channel MOSFET 202 of the transducer drive circuitry 20 is generated with −HV, as a reference potential. The current pulse signal generated by the voltage-to-current converter 106, described as above, is again converted into a voltage pulse signal by a resistor R13 of the block 150. If a mirror ratio of the current mirror circuit 146 is 1:1, a swing of the voltage pulse converted by the resistor R13 is expressed by (VDD−2*Vgs)*R13/R8. This voltage pulse is an input voltage to a buffer 154 of the block 150, and a swing of the voltage pulse is normally set to the same as VGSn. Since a swing of an output voltage GP of the buffer 154 is the swing for driving the gate of the high voltage resistant n-channel MOSFET 202, as described above, the swing of the output voltage GP need be VGSn, and a high level output voltage −HV+VGSn decided at a node 156 of the buffer 154, is generated in the block 152. The block 152 comprises a current mirror circuit 158, resistors R11, R12, capacitors C3, C4, a high voltage resistant p-channel MOSFET 160, and a high voltage resistant n-channel MOSFET 162. Current flowing to a copy source of the current mirror circuit 158 is expressed by (VDD−2*Vgs)/R11. This Vgs refers to a gate—source voltage of a low voltage resistant p-channel MOSFET as a constituent of the current mirror circuit 158. If a mirror ratio of the current mirror circuit 158 is 1:1, a potential at a node 164, converted by the resistor R12, is expressed by −HV+(VDD−2*Vgs)*R12/R11. The potential at the node 164 is decided such that a potential at the node 156 turns to −HV+VGSn, as described above. More specifically, R11, and R12 are decided so as to satisfy (VDD−2*Vgs)*R12/R11=VGSn+Vgs162. This Vgs162 refers to a gate—source voltage of the high voltage resistant n-channel MOSFET 162 to execute operation as a source follower. The high voltage resistant p-channel MOSFET 160 is inserted to prevent a high voltage not lower than a absolute rating from being applied between the source and the drain of a low voltage resistant p-channel MOSFET as a copy destination of the current mirror circuit 158, and the resistors R9, R10 are set such that the gate potential expressed by R10/(R9+R10)*VDD can cause the high voltage resistant p-channel MOSFET 160 to adequately operate, as is the case with the high voltage resistant p-channel MOSFET 148. The capacitor C3 is inserted for the purpose of stabilization of a gate potential of the high voltage resistant n-channel MOSFET 162. The capacitor C4 is inserted between the node 156 as an output of the source follower, and −HV, functioning as a bypass capacitor for supplying instantaneous carrying current consumed by the buffer 154 with an output drive capacity thereof, enhanced to drive the gate of the high voltage resistant n-channel MOSFET 202.

With the current mirror circuits 146, 158, +VDD is a source side reference voltage, so that the signal path from the input logic control terminal INN of the high voltage Nch MOSFET to the high voltage resistant n-channel MOSFET 202 can be operated as a channel as a damper of −HV=0 V, and −HV is optionally variable in the range of 0 V on the order of ±200 V.

Subsequently, the transducer drive circuitry 20 is described hereinafter. In FIG. 2, the transducer drive circuitry 20 comprises the high voltage resistant p-channel MOSFET 200, the high voltage resistant n-channel MOSFET 202, the high voltage resistant diodes 204, 206, the resistors 208, 210, and the Zener diodes 212, 214. The respective gates of the high voltage resistant p-channel MOSFET 200, and the high voltage resistant n-channel MOSFET 202 are driven by the respective output voltage pulses at the nodes GP, GN of the MOSFET gate drive circuitry 10, as described previously.

As shown in FIG. 3, a multi-channel integrated driver circuitry is made up by providing a plurality of (1 to n) of channels, a driver comprised of the MOSFET gate drive circuitry 10, and the transducer drive circuitry 20, in pairs, serving as a unit of the channel, and by integrally forming n pieces of the drivers corresponding to the plurality of the channels 1 to n, respectively, on a single semiconductor substrate. More specifically, because there is the case where the present ultrasound pulser can be implemented with the circuitry shown in FIG. 1, as a unit channel, by adoption of a configuration wherein a plurality of outputs OUT of channels as drivers, and channels as dampers are short-circuited with each other, the output signal is separated between different channels by adoption of a configuration wherein respective drain outputs of the high voltage resistant p-channel MOSFET 200, and the high voltage resistant n-channel MOSFET 202 are short-circuited with each other via the high voltage resistant diodes 204, 206, respectively, to be turned into one output OUT. The resistors 208, 210, and the Zener diodes 212, 214 are inserted for the purpose of protecting the high voltage resistant p-channel MOSFET 200, and the high voltage resistant n-channel MOSFET 202, respectively, from an overvoltage being applied between the gate and the source thereof.

Thus, with the present invention, it is possible to implement a monolithic IC wherein a plurality of channels are formed on a single semiconductor substrate such as a monocrystalline silicon with the use of the driver capable of output burst operation, and damper operation, in form protruding upward and downward, in the range of 0 V on the order of ±200 V, as shown in FIG. 1, serving as a unit of the channel.

The present embodiment can be carried out even by adoption of a configuration that can be driven with a voltage output pulse in either polarity, in the form protruding either upward, or downward, in FIG. 1, more specifically, even by use of only the signal path from the input logic control terminal INP of the high voltage Pch MOSFET to the resistant p-channel MOSFET 200, or only the signal path from the input logic control terminal INN of the high voltage Nch MOSFET to the high voltage resistant n-channel MOSFET 202.

Further, if the present embodiment is carried out by use of the configuration wherein the plurality of the outputs OUT are short-circuited with each other, as shown in FIG. 3, it is possible to output a quasi-Gaussian waveform higher in quality than a burst waveform with the use a combination of the plurality of the channels adequately set to different ±HV, respectively, serving as one channel.

Further, with the present embodiment, since other types of transistors such as a bipolar transistor, and an IGBT can be substituted for the high voltage resistant p-channel MOSFET 200, and the high voltage resistant n-channel MOSFET 202, in the transducer drive circuitry 20 of FIG. 1, those MOSFETs can be used as a driver circuit for current-driving an output load besides a high voltage pulse generation circuit according the present embodiment.

As described hereinbefore, according to the present embodiment, an ultrasound pulser (a driver circuitry) having an output pulse swing variable range of 0 V on the order of ±200 V, suitable for application to a medical ultrasound system, can be implemented in a form aiming at not only reduction in the number of necessary terminals, per a unit channel, and relaxation of restrictions on mounting, owing to elimination of needs for external capacitors, by DC-coupling of the MOSFET gate drive circuitry with the transducer drive circuitry, but also reduction in semiconductor substrate area per the unit channel by use of low voltage resistant transistors wherever possible. In so doing, there can be obtained an advantageous effect of implementing a semiconductor integrated circuit device with a plurality of channels integrated on a small chip area. 

1. A semiconductor integrated circuit comprising: a pair of input terminals; a first drive circuitry connected to said pair of terminals to convert a first voltage pulse signal, having a first reference potential and being inputted from said pair of input terminals, into a second voltage pulse signal having a second reference potential higher than the first reference potential to be thereby outputted; a second drive circuitry connected to a pair of outputs of said first drive circuitry to generate a fourth voltage pulse signal with a voltage swing based on a potential difference between the second reference potential and a ground potential to drive an external output load on the basis of the second voltage pulse signal being inputted from the pair of outputs of said first drive circuitry to be thereby outputted; and an output being commonly connected to a pair of outputs of said second drive circuitry to output the fourth voltage pulse signal being outputted by said second drive circuitry to the external output load, wherein said first drive circuitry is integrated with said second drive circuitry monolithically into a single semiconductor substrate, wherein the pair of outputs of said first drive circuitry are mutually DC-coupled with a pair of inputs of said second drive circuitry, respectively, and wherein said first drive circuitry includes: a pair of voltage-to-current converters to convert a third voltage pulse signal based on the first voltage pulse signal into a current pulse signal, respectively; and a pair of current-to-voltage converters to convert the current pulse signal, being inputted from respective outputs of said pair of voltage-to-current converters, into the second voltage pulse signal, respectively, such that reference potentials of the respective current pulse signals are changed from the first reference potential to the second reference potential.
 2. The semiconductor integrated circuit according to claim 1, wherein said second drive circuitry has a voltage resistance higher than that of said first drive circuitry.
 3. The semiconductor integrated circuit according to claim 2, wherein said first drive circuitry further comprises a pair of voltage level translators interconnecting said pair of input terminals with respective inputs of said pair of voltage-to-current converters, respectively, and wherein the first voltage pulse signal having the first reference potential and a first voltage swing is converted into the third voltage pulse signal having the first reference potential and a second voltage swing through the respective voltage level translators.
 4. The semiconductor integrated circuit according to claim 3, further comprising: a first power supply voltage terminal, made up such that a first power supply voltage is applied thereto; a pair of second power supply voltage terminals being made up such that a second power supply voltage higher than the first power supply voltage is applied thereto, respectively; and a pair of third power supply voltage terminals being made up such that a third power supply voltage is applied thereto, respectively, wherein each of said pair of voltage level translators of said first drive circuitry is connected to both of said first and third power supply voltage terminals, wherein said pair of voltage-to-current converters of said first drive circuitry are connected to said pair of third power supply voltage terminals, respectively, wherein said current-to-voltage converters of said first drive circuitry are connected to said pairs of second and third power supply voltage terminals, respectively, and wherein said second drive circuitry is connected to said pair of second power supply voltage terminals, respectively, said second drive circuitry generating the fourth voltage pulse signal out of the second power supply voltage applied to said second drive circuitry via said pair of second power supply voltage terminals, on the basis of the second voltage pulse signal.
 5. The semiconductor integrated circuit according to claim 4, wherein an input gate voltage swing of said second drive circuitry is generated by an internal power supply circuit including a source follower, in the respective current-to-voltage converters of said first drive circuitry on the basis of the second power supply voltage.
 6. The semiconductor integrated circuit according to claim 1, wherein the output load is an ultrasonic transducer, said second drive circuitry is a transducer drive circuitry for driving the ultrasonic transducer, and said first drive circuitry is a MOSFET gate drive circuitry for driving high voltage MOSFET gates, making up the transducer drive circuitry, an ultrasound pulser for a medical ultrasound system being comprised of the MOSFET gate drive circuitry, and the transducer drive circuitry.
 7. The semiconductor integrated circuit according to claim 6, wherein a plurality of channels are provided, the ultrasound pulser comprised of the MOSFET gate drive circuitry, and the transducer drive circuitry serving as one unit of the channel, and a plurality of the ultrasound pulsers corresponding to the plurality of the channels, respectively, are integrally formed on a single semiconductor substrate.
 8. A semiconductor integrated circuit comprising: a first drive circuitry having a first voltage resistance; and a second drive circuitry connected to a back stage of the first drive circuitry, having a second voltage resistance higher than the first voltage resistance, wherein the first drive circuitry includes voltage-to-current converters for converting an input voltage signal having a first reference potential into a current signal, respectively, and current-to-voltage converters for converting the current signal into a voltage signal having a second reference potential higher than the first reference potential, respectively.
 9. The semiconductor integrated circuit according to claim 8, wherein the voltage signal with a voltage pulse swing based on an output voltage keeping a fixed difference from a voltage necessary for driving the second drive circuitry is outputted to the second drive circuitry.
 10. The semiconductor integrated circuit according to claim 9, wherein the first drive circuitry further includes voltage level translators, connected to respective inputs of the voltage-to-current converters, and is made up such that a first voltage pulse signal as received, having a first reference potential, is converted into a second voltage pulse signal having a second reference potential higher than the first reference potential before outputted, and wherein the first voltage pulse signal having the first reference potential, and a first swing is converted into a third voltage pulse signal and a second swing through the respective voltage level translators, and the third voltage pulse signal is converted into the second voltage pulse signal through the respective voltage-to-current converters, and the respective current-to-voltage converters.
 11. The semiconductor integrated circuit according to claim 10, further comprising: a pair of first power supply voltage terminals, made up such that a first power supply voltage is applied thereto, respectively; a pair of second power supply voltage terminals, made up such that a second power supply voltage higher than the first power supply voltage is applied thereto, respectively; and a pair of third power supply voltage terminals, made up such that a third power supply voltage is applied thereto, respectively, wherein the first drive circuitry are connected to the first, second, and third power supply voltage terminals, respectively, and the second drive circuitry is connected to the second power supply voltage terminals, and wherein the second drive circuitry generates a fourth voltage pulse signal out of the second power supply voltage applied to the second drive circuitry via the second power supply voltage terminals, on the basis of the second voltage pulse signal.
 12. The semiconductor integrated circuit according to claim 11, wherein an input gate voltage swing of the second drive circuitry is generated by an internal power supply circuit including a source follower, on the basis of the second power supply voltage applied to the second drive circuitry.
 13. The semiconductor integrated circuit according to claim 8, wherein the second drive circuitry is a transducer drive circuitry for driving an ultrasonic transducer, the first drive circuitry is a MOSFET gate drive circuitry for driving high voltage MOSFET gates, making up the transducer drive circuitry, an ultrasound pulser for a medical ultrasound system is comprised of the MOSFET gate drive circuitry, and the transducer drive circuitry, a plurality of channels are provided, the ultrasound pulser comprised of the MOSFET gate drive circuitry, and the transducer drive circuitry serving as one unit of the channel, and a plurality of the ultrasound pulsers corresponding to the plurality of the channels, respectively, are integrally formed on a single semiconductor substrate.
 14. A semiconductor integrated circuit comprising: a first drive circuitry having a first voltage resistance; and a second drive circuitry connected to a back stage of the first drive circuitry, having a second voltage resistance higher than the first voltage resistance, wherein the first drive circuitry is made up so as to be operated by first, second, and third operating voltages, respectively, having a circuit for generating a second potential having a predetermined potential difference on the basis of a predetermined third potential.
 15. The semiconductor integrated circuit according to claim 14, wherein the second drive circuitry is operated at the second potential as an operating voltage, and wherein signal transmission from the first drive circuitry to the second drive circuitry is executed by respective voltage-to-current converters, for converting an input voltage signal into a current signal, and respective current-to-voltage converters, for converting the current signal into a voltage signal.
 16. The semiconductor integrated circuit according to claim 15, wherein the first drive circuitry further comprises voltage level translators, connected to respective inputs of the voltage-to-current converters, and is made up such that a first voltage pulse signal as received, having a first reference potential, is converted into a second voltage pulse signal having a second reference potential higher than the first reference potential before outputted while the first voltage pulse signal having the first reference potential, and a first swing is converted into a third voltage pulse signal and a second swing through the respective voltage level translators, and the third voltage pulse signal is converted into the second voltage pulse signal through the respective voltage-to-current converters, and the respective current-to-voltage converters.
 17. The semiconductor integrated circuit according to claim 16, further comprising: a pair of first power supply voltage terminals, made up such that a first power supply voltage is applied thereto, respectively; a pair of second power supply voltage terminals, made up such that a second power supply voltage higher than the first power supply voltage is applied thereto, respectively; and a pair of third power supply voltage terminals, made up such that a third power supply voltage is applied thereto, respectively, wherein the first drive circuitry are connected to the first, second, and third power supply voltage terminals, respectively, and the second drive circuitry is connected to the second power supply voltage terminals, and wherein the second drive circuitry generates a fourth voltage pulse signal out of the second power supply voltage applied to the second drive circuitry via the second power supply voltage terminals, on the basis of the second voltage pulse signal.
 18. The semiconductor integrated circuit according to claim 17, wherein an input gate voltage swing of the second drive circuitry is generated by an internal power supply circuit including a source follower, on the basis of the second power supply voltage applied to the second drive circuitry.
 19. The semiconductor integrated circuit according to claim 14, wherein the second drive circuitry is a transducer drive circuitry for driving an ultrasonic transducer, the first drive circuitry is a MOSFET gate drive circuitry for driving high voltage MOSFET gates, making up the transducer drive circuitry, an ultrasound pulser for a medical ultrasound system is comprised of the MOSFET gate drive circuitry, and the transducer drive circuitry, a plurality of channels are provided, the ultrasound pulser comprised of the MOSFET gate drive circuitry, and the transducer drive circuitry serving as one unit of the channel, and a plurality of the ultrasound pulsers corresponding to the plurality of the channels, respectively, are integrally formed on a single semiconductor substrate. 